The overall objective of this work is to define the mode of action of endotoxin at the cellular level. Two cell types of murine origin are to be investigated: 1. The B lymphocyte and 2. the normal and exudate macrophages. Radiolabeled endotoxin of high specific activity and highly purified will be prepared. The binding of this to B cells vs. T cells, will be measured and the extend of binding correlated with both mitogenesis and immunoglobulin production. RNA synthesis in endotoxin stimulated B cells will be quantitated. The relationship of messenger RNA production of early interferon by mouse spleen cells stimulated in vitro will be measured. The cell source, i.e., lymphocyte, macrophage, or both will be defined and the relationship of interferon release to the production to RNA synthesis investigated. The effects of various doses of endotoxin and/or corticosteroids on the activation of macrophages in vitro will be studied. The effect of these agents on the macrophage functions; pinocytosis, phagocytosis, exocytosis of enzymes, RNA synthesis, and tumor killing will be measured.